Method and apparatus for casting metal



Dec. 17, 194i). N. P. Goss METHOD AND APPARATUS FOR CASTING METALOriginal Filed July 29, 193'! 3 Sheets-Sheet l FI Grl uw /Vcu RO oG n m.m EP /o v NN Mdm m) Dec. 17, 1940. N, P, Goss uETHon Arm APPARATUS FORcAs'rIuc `MFTAL.

`3 SheetS-Sheet 2 original Filed July 29, 1937 INVENTOR NORMAN P. Gossnga 17, 1940.

N. P. Goss 2,225,373

METHOD AND APARATUS FOR CASTING METAL Urignal Filed July 29, 19257 3Sheets-Sheet 3 Fla-4 INVENTOR VNORMAN P. GOSS Patented Dec. i7,

PATENT oFF-TCE METHOD AND APPARATUS FOR CASTIN l METAL Norman P. Goss,Youngstown, Ohio Application July 29, 1937, Serial No. 156,327

` Renewed May '1, 1940 Claims.

This invention relates toca method and apparatus for continuouslycasting metals.

My invention provides a method and apparatus' for passing astream ofmolten metal into a die and extruding or extracting a continuous memberof solid or seuil-solid metal from the other end of the die. I am awarethat methods and apparatus for a similar purpose have been heretoforeproposed but. where they purported to deal 0 with metals of high meltingtemperature, such as steel and the like, they were of no practical orcommercial value because, if successful at all,

after a brief operation the apparatus broke down.'

due to the freezing of thegmetal at such points as 5 to stop theprocess, or because of the disintegrato provide a novel die in which themolten metal ,is cooled and a skin cast upon it, and wherein a substanceis provided between the walls of the die and the cast metal whichperforms a number of functions, among them being the lubrication of thepassage of the metal through the die, the filling of the spaces wherethe solidifying metal draws away from the die bya self-accommodatingmaterial which maintains efcient heat conductivity between the metal andthe die, the protection of the walls of the die from direct contact withand heat radiation from the metal, and the maintaining of a suitablesurface on the cast metal. One preferred form of such a lubricant orself-accommodating die lining material is graphite, which is a goodblack body and performs the function of absorbing and conducting heatfrom the solldifying metal to the walls of the die while reecting backto the metal little of the heat received, this in addition to performingall of the functions outlined just above.

Another feature of the present invention is the provision of apparatusfor very carefully controlling the temperature of the metal during allstages of the casting process.` This temperature control extends to themetal in the reservoir from which molten metal is fed to the casting orchilling apparatus and to the various parts of the apparatus as themetal passes through it. By

such close control the metal may be cast from a point just slightlyabove the solidus, giving certain preferred characteristics to thesolidified metal where desired. Also the rate of contraction and thecorrespondence of the sectional area of the cast metal to the die isassured at all points during the passage of the metal through the die.This assures a predetermined space for accommodating the die liningmaterial such as graphite mentioned above.

Another feature of my process and apparatus is the special arrangementat the molten metal receiving end of the die where special means isprovided for confining the molten metal while the rst skin is beingformed thereon. This feature involves the use of a member or means whichis hereinafter termed a liner, the use of which is very important incontrolling the formation of the first skin on the solidifying'metal. Bythe use of varying types of liners the texture of this skin may bevvaried as will hereinafter appear. The use of such a liner contributesto the long life and commercial practiability of* iny die castingprocess.

Another object of the Ypresent invention is to provide novel means forinsuring the steady and continuous passage of the metal through theidle,

both by means of the hydrostatic pressure of molten metal is heldpreferably in a reservoir of sufficient capacity to provide a steadystream of molten metal to the die apparatus at a substantially constanttemperature. Such a reservoir is also of. sumcient capacity to permitthe molten metal to lie quietly so that slag and other occluded foreignmaterial may have time and opportunity to rise to the surface where itmay be disposed of. Another novel feature which protects the quality ofthe metal is the provision of nonoxidizing and, where desired, areducing atmosphere about the metal as it passes into the die and as itpasses through the die. This prevents the formation of oxides during thecourse of the casting process which oxides might be occluded vin thesolidified metal or might appear upon the surface thereof with not onlybad effects upon the metal quality but deleterious eifects upon thewalls of the die. Y

Another function of the'application of nonoxidizing or reducing gasesabout the solidifying metal as it passes through the die is theprotection which certain of such gases may provide for the walls of thedie and the aid of such gases as for instance hydrogen, in maintainingheatconductivity between the solidifying metal and the walls of the die.l

Another novel feature of my apparatus is the provision of nonoxidizingor reducing gases in such a way in the apparatus that they not onlyprovide the advantageous features pointed out above but in addition maybe arranged to bubble through the molten metal in the feeding reservoirthereby producing a metal agitating or cleanmetal and the walls of thedie without distorting or damaging the `solidifying skin on themetalthrough the die. l

Another novel feature of the present invention is the carefulconstruction of the walls of the die to conform to the cross section ofthe solidifying `and contracting metal passing therethrough.

Among the novel features of my invention is the provision of a metalconstricting portion at the exit end of the die whereby to reiine thecrystalline structure of the metal at that point and to protect thesemi-solid metal in the die from the pulling effect of the pinch rollsor other pulling apparatus which may be used to aid in the passage ofthe metal out of the die.

Other advantages and novel features of my method and apparatus willappear hereinafter from the speciilcation and the drawings and theessential features thereof will be summarized in the claims.

In the drawings:

Fig. 1 is a central section showing typical apparatus for carrying outmy novel casting process with certain portions thereof relative totemperature control being shown somewhat diagrammatically;

Fig. 2 is an enlarged central section through the die portion of Fig. 1and along the line 2-2 of Fig. 3, with lubricant supply and dietemperature control shown diagrammatically;

Fig. 3 is a sectional view along the lines 3-3 ofFigs.2and4;

Pig. 4 is a sectional view along the line 4-4 of .Fis-3:

ly controlling the temperature of the molten metal'in thereservoir inaccordance with a predetermined temperature of metal passing to the'die;

Fig. 7 is a section similar to Fig. 3 showing a modified form of die forforming shapes directly from molten metal.

In the apparatus illustrated in Figs. 1 to 6, a reservoir I0 is providedfor receiving and holding molten metal before it is fed to the castingapparatus. Such. a reservoir will be supported upon suitable buildingstructure (not shown) and supplied with molten metal from a ladlehandled by an overhead crane, or by any other suitable apparatus. The.reservoir i0 is o! such capacity that a body of metal is held inasubstantially quiet state and at a substantially constunt temperaturefor feeding to the 'casting apparatus. The device of Figs. i to 6illustrates apparatus for casting slabs and where such slabs are ofnormal heavy section, such as 2 to 6 inches thick and 12 to 36 incheswide or wider, the reservoir In would hold to `80 tons or more of metalto provide the. highest quality of cast metal. l y

The reservoir illustrated comprises a steel or cast iron shell providedwith an inner refractory lining Il adapted to stand the heat of themetal in the reservoir for long periods of time without substantialdeterioration, or objectionable effect upon the metal in the reservoir.For instance, if molten steel is to be handled, `the lining might be ofchrome brick. If the metal in the reservoir` is to `be held at acarefully determined temperature and if skulls in the reservoir are tobe avoided, sorneheating means should be provided therefor. In the formshown an induction coil I2 is built into the reservoir protected by aheat protecting refractory layer I3 between the coil and the innerlining and preferably having also outside of the coil a heat insulatinglayer Il next to the shell. The reservoir may also be provided with anoverflow spout (not shown) 'near the top so that upon an accumulation ofslag in the reservoirthe level of the metal therein may beraised and theslag run off through the spout.

Suitable openings are provided for removing metal from the bottom of thereservoir lil. A mainopening lileading to the casting apparatus isclosed by the usual stopper I6 which is manipulated by `the stopperhandle I1. Also preferably an auxiliary or emergency outlet I8 isprovided in the bottom of the reservoir closed by the stopper Il whichmay be manipulated by the handle 2li. If for any reason the reservoirmust be emptied other than through the opening l5, the outlet Il isavailable through which the metal in the reservoir might be passed toanother ladle or toa series of molds if necessary to discontinue theoperations through the continuous casting apparatus.

The metal passes from the feed reservoir I0 through a passage 2| to thecasting apparatus. This e is preferably lined also with a refractorylining and preferably also supplied with a separate electric inductionheating coil 22 supplied from a suitable source of current. This willinsure that the passage 2i remains open at all times.

The diecasting apparatus is indicated generally at 23 and comprises anupper chamber portion '2l adapted to be connected to the passagerway 2ito receive metal from the reservoir l0.

Below this is the die portion 25 where the initial solid skin is formedon the metal. Again below this is the die portion 26 for the furthersolidiflcation of the metal on its passage therethrough. At the mouth ofthe die is theporticn 21 whichis somewhat restricted so as to provideametal working eect and `to protect the metal farther back in the diefrom any` pull exerted by the extracting apparatus. This pcrtlonalsohelps to keep the shape centered in the die. A pair of pinch rolls forextracting is indicated somewhat diagrammatically at 2l, it beingunderstood that. these will be provided with a suitable drive and withmeans for varying the position of therolls on opposite sides of the slabof metal passing. between them. Suitable structural framework (notshown) will be provided for supporting the die casting apparatus.

Where the passageway 2l leads to the upper chamber oi' the die castingapparatus, a structure is preferably provided enabling an 'inspection of'the flow of metal into the die so .that the operator may determine boththe level of the metal in the dieand the temperature of the flowingmetal. To this end an upwardly extending passageway 29 is provided at'this upper end with a suitable inspection window 30 adapted towithstand the high temperatures present. Through this window thetemperature of the metal may be read by an optical pyrometer if desiredor a light sensitive cell may be placed there as indicated at 3i for thepurpose of automatically regulating the temperature of the metal in thereservoir in accordance with the temperature or the met-a1 sowing to thedie. A suitab1e control circuit for this purpose is indicated in Fig. 6and will be hereinafter more fully explained.

Preferably the die casting apparatus is connected with the metalreservoir and associated parts in a manner to be detached if necessary.

To this end the case 32 housing the passage connected with the,reservoir i0 is provided with outwardly extending anges 33 at the lowerend, which anges are bolted at 34 to brackets 35 of the casing 36surrounding chamber 24. 'Ihis die portion preferably has a refractorylining 31.

The die casting portion 25 comes in contact with the molten metal duringthe formation of the-first outer skin. This die portion has waterpassages 25a through which a stream .of water is continuously passed forthe pllIpOse of chilling the die to whatever extent may be desirable.

Between the die portions 25 and 26 a machined joint 38 may be provided,or a gasket of suitable material, for instance asbestos, may be insertedthere. These two die portions are secured together by their anges as bythe use of bolts 39, clamps or the like. One of the novel features of myinvention is the provision of a. liner 40 in this upper portion of thedie where the molten metal rst cornes in contact with the inner wallsthereof. This liner must be a good heat conductor and have goodrefractory characteristics and should have little chemical action uponthe metal in contact with it. Preferably also for long life it should behighly resistant to abrasion of the molten metal. Quite a number ofmaterials are suitable for this liner, among them tungsten carbide,silicon carbide, graphite, graphite in copper, graphite and carborundum,carborundurn alone, chrome brick, chrome copper alloys, nickel copperalloys, suchas InconeP' with or Without metallic oxide additions, highchrome steels. Monel metal with or Without chromic oxide, Monel metalwith graphite, and similar materials. I prefer to make this liner dil,as thin as is consistent with long life so that the heat conductivitytherethrough to the cooled copper Wall will be suiiicient to i'orm askin on the metal.

I find that the surface qualities of the metal may be varied accordingto the choice of the type of liner et. For instance a graphite andcarborundum liner will give a rough texture to the surface while Monelmetal or tungsten carbide liners give a smooth surface.

The die portion 2e may be of one or more sections. -As illustrated Ihave shown one section split alonga vertical plane into two halves whichare machined and bolted together by their ilanges 28e. This die portionis provided 'with water cooling passages 28a. The metal-contacting innerfaces ofthe copper walls 28h ii' desired may be formed of graphite incopper so as to harden land increase the life of the inner' surface ofthis portion of'the die.

While not absolutely necessary to the practical operation oimy diecasting operation, I prefer to supply at the exit end of the die themetal constricting portion 21. As shown here, this is preferably of aharder material than the die portions 26. For instance this might be ofa harder copper than the rest of the die or preferablywould be of chromenickel steel or the like and provided the substantially solidiiied metalis pulled out of the die as for instance by the pinch rolls 2B. Thisprevents any ltearing of the semi-solidified metal in the upper portionof the die.

'I'he die portions 26 and 21 may be secured together as by theiroutwardly extending end flanges and by bolts 4i.

Preferably means is provided for so controlling the ow of water throughthe water cooling pas;-`

sages of the die as to provide a constant rate of cooling of the-metalas it passes through the various portions of the die. If this is donethe physical characteristics of the solidified metal will be heldconstant because of the constant cooling characteristics throughout thelength of the die as the metal progressively passes therethrough. Tothis end I have indicated Asomewhat; diagrammatically in Fig. 2, a.manner of sectionalizing the water cooling of the die and the automaticcontrol of the temperature of each section. To. this end the coolingpassages 25a, 26a, and 21a. are supplied with a cooling medium such aswater or the like fromsources 42, and discharge is at 43. Preferablyeach of these die cooling sections is provided with means forcontrolling the iiow of cooling medium in response to the temperature ofthe die walls so as to maintain constant casting conditions. Athermostatic valve 44 is operated by a solenoid 45 which is controlledby a relay 46- which in turn is responsive to the thermostat pyrometer41 having a pyrometer element embedded in the Wall of the die. Asuitable power source is connected at 48 for operating the thermostaticvalve and the arrangement of the f parts is such that if the temperatureof the pyrometer element 41 rises above a predetermined point, the valve44 will be opened to admit more cooling medium to the cooling passages,and upon the pyrometer dropping below the predetermined high point thesolenoid l5 will be deenergized permitting the valve dfi to return to apredetermined minimum setting. Other speciiic arrangements of thecontrol system for thecooling medium will occur to those skilled in thisart and any suitable system is within the scope of my invention.

A suitable control system for holding the metal in the reservoir i@ at asubstantiallypconstant temperature is shown' in Fig, 6 where theelectric.

furnace high frequency'coil i2 is indicated diagrammatically as beingsupplied with current of high voltage and `highfrequency from a`suitable source 49. In the supply line` for coll l2 is a relay SIIhaving a contact `Sila and a contactor arm lIlb controlled by` the relaycoil. The `contact. `50a is shown diagrammatically and willbe onesuitable for the current and voltage handled. When the `control `circuitcomes from the secondary, of a transformer connected with a suitablesource of alternating current. A rectifier `Il provides a direct currentbetween the conductors Il and 56.

` The line 56 is connected through lines `ITI and 58 so as to energizethe coil of :relay `and I8 is 'connected with the anode B2b of thetriode. The

cathode 52e isconnected through 'resistance 59 and line GII with line `Band slalso connected through line i I and resistance 62 with the line55;

Between lines 5I and 6I` is connected the vari-` able resistance i3.AThe line B4 connects line Bly and the other terminal of the lightsensitive cell IIb. By suitably varying the aperture of the lightsensitive cell and the adjustment ofrthejvariable resistance 63, the`cellmay be set to energize the circuit whenthe temperature' of themetal ilowing into the die castingapparatus drops below a pre-`determined point yso as to close theirelay Il and the other hand, if toprovide high frequency current'to the coil I2 until the temperature `ofthe `metal flowing into the die casting apparatus passed a predeterminednigh point at which time the iight sensitive een would be energized andarranged to break contact at relay il `instead of making contact asillustrated in Fig. 6. It will be understood'of coursel that two lightsensitive cells might be supplied.

one to cut ofi' the supply of current'to coil I2 if the metal passedabovea predetermined high;

be indirect, that is, from the metal being cast through the die wall tothe cooling medlunn Most i metalsshrinkor contract whencooled. This reisuits in a Vdrawingaway of the metalvfrom the cooling walls of the dieleavingan air gap across i which heat transfer is greatly retarded.

`It has `been assumed, also, that one faced with the dilemma of the airgap between the cool- I ing walls and ,thehot` metal (as mentionedabove) with consequent loss of heat transfer, or die walls which arearranged to bein close contact `with the hot'metal with consequentfriction so great I tively high thermalfconductivity so as to mi andkeep nlled along the length of the die the shrink- At the same time,this material maybe so selected that it has `lubricating vproper-tieseven at the temperature of,` steel iustbelow thesolidus.

Graphite is such a material.` Thus thermal conductivity is increased andfriction reduced.

Here Q representsthe quantity of heat passing `through a material ofarea A and thickness d and having a coeilicient of thermal conductivityK in `the time t, where the opposite faces of the material are subjectto temperatures Ti and T: respectively.` t i The coemcient K" forgraphite approaches that `of steel at high temperatures just aftersolidifying. Therefore. if graphite illls the space left by contractionof the first-formed steel skin away from the die wall, the `transfer ofheat from the `metal to the wall will continue at almost the same.mately one-ilftiethof the graphite.I 1

Another effect 1 of my improvedA` method and apparatus is anincreaseduniformity in the cast metal. Without the use of my improvedapparatus the contraction of the 'metal from `the walls supply currentto the high frequency coil I2.` 0n` of the idie'leaves the metal incontact with the ydesired the cell might be set` walls at some point andout ofcontact at other points; giving aY very irregular and nonuniform Iage cavity caused bythe cooling of the cast metal.

cooling effect with resultant inequalities and imperfections in themetal and very seriously aifect.. ing the life of the die:`

For all of the various reasons previously set forth herein such as lossof heat conducting contact between the metaland the die, hre cracks inthe I find that the above named Vfilling materials are best introducedbetween the metal and the die wall ina nnely divided or powdered formeither dry or carried by asuitable vehicle. Hereafterin thespecification and claims, the use of i the term powdered" doesk notnecessarily refer the first skinhasformed onthemetal and I' desire toinclude all suitable materials which will withstand the high`temperatures met with at this point and yet which will accommodateitself to the interstices and changing movements between the skin of themetal and the die walls and which will maintain substantially continuousheat conducting contact between the congealing metal and the die walls.

Where' steel is being continuously ast in my novel apparatus I findgraphite is particularly applicable because it readily conforms to theinterstices between the metal skin and the inner walls of the die. andit has very high heat conductivity. Furthermore the graphite isaI goodblack body and absorbs heat from the steel vat high temperatures andconducts this heat to the die walls without reecting back upon the steelmuch of the heat received. The graphite has the additional merit that itcontributes -to a smooth surface on the cast steel, remains on the caststeel as a protective film while it cools, and protects the die fromheat otherwise radiated from the lsteel'which would produce re cracksand deterioration of the die walls.

After the first thin skin has formed on the metal and it shrinks awayfrom the die wall, if an air gap is present as in the prior art, thethin skin is insuiiicient to support the interior molten mass and thepressure of molten metal above it. The skin is thus subject todistortion and may rupture. Also, if conductivity between the new skinand the cooler die wall is broken by the air gap, the skin is reheatedfrom the molten interior and may remelt in spots causing bleeding. Thiswill produce surface defects and possibly a spongy center. My vinventionsupplies a plastic material which lls this space where the air gap wasin the prior art between the thin skin and die wall. 'Ihis plasticmaterial maintains thermal conductivity between the metal and die so asto prevent reheating of the skin, and supports the thin skin so as toprevent distortion and rupture.

Any suitable means may be provided for applying the self-accommodatingdie lining film hereinafter designated lubricant Some oi the materialsmay be suitably applied by the .use of a power driven screw asillustrated diagram matically in Fig. 2. Here a spiral screw 65 ishoused in a cylindrical casing 65 supplied with lubricant material froma source 6l and the screw is driven through gears 68 operated from avariable speed motor 69. This will supply lubricant under pressure tothe conduits 1G, the pressure being varied by varying the speed of motor69. One arrangement of these conduits is shown in the drawings but otherarrangements may be used so long as the lubricant is fed to all sides ofthe cast piece under suiiicient pressure to enter the spaces between thecast piece and the die wal s.

For other lubricants a plunger pump may be used having a bypass openingat a predetermined pressure so that the pump may be run to supplylubricant at any desired pressure. Other materials may be supplied fromreservoirs of lubricant vunder pressure such as that supplied from apower driven plunger or. compressed air to supply the lubricant throughsuitable conduits l to the die. Certain of the lubricants may be mixedwith glycerine or other suitable liquid to give them sufcient fluidity.

One form of passageway which I have conceived as suitable for applyingthe lubricant graphite is illustrated in Fig. 5 Where a groove 'Hextends substantially continuously around the inner face of the die walland is supplied at spaced points vthrough conduits l2 in the die wallsconnected with the pressure conduits 'lli heretofore described. In sucha construction suficient connections l2 are provided to maintain acontinuous supply of graphite about the inner periphery of the die ateach point selected. The

pressure on the lubricant will be so regulated that at the point 13,Fig. 5, the skin formed onl the solidifying metal 14 will ,not bedeformed to any great extent. In other words the graphite will formsubstantially a continuation of the inner face of the-die at this pointand a small lm will be carried alongside the metal as indicated at 15lling the interstices between the metal and the die wall. This view issomewhat distorted to illustrate the formation of the lubricant lmbetween the. cast piece and the die wall. As shown in the various viewsall of the lubricant passages will preferably be arranged with smoothcurves so as not to interrupt the ow of the lubricant.

To protect from oxidation the metal flowing from the reservoir I0through the passage 23 to the die casting apparatus, I may supply to theupper end of the die casting apparatus a suitable gas under pressure asat the connection 16, Fig. 1.

Suitable gases for this purpose are for instance hydrogen. nitrogen,carbon monoxide, carbon dioxide and others which will occur to thoseskilled in this art. These gases may simply be inert gases as nitrogenor may have a reducing eiect as hydrogen. In the case of nitrogen,oxidation of the molten metal previous to its solidiiication wouldsimply be prevented. In the case of hydrogen not only would this sameeiect be produced but any small amounts of metallic oxides present inthe upper portion of the die casting apparatus would be reduced. Thisprevents` the formation of oxides in the die casting apparatus whichwould have a bad effect upon the physical characteristics of the metaland also upon the surface characteristics of the cast metal and the diewalls.

The gas supplied at source 'l5 may be under sulcient pressure to createconsiderable hydrostatic pressure in the upper portion of the die so asto aid in the passage of the metal through the die and to give acompressing eiect upon the cast metal so as to refine the grainstructure thereof. I believe it is novel to act upon the one end of thecast piece with gas under pressure while pulling the other end oi thecast piece as by the pinch rolls 2B and lubricating the passage of themetal through the die. I thus powerfully urge the cast piece through thedie without tearingthe metal.

The gas supplied from source 'it may be placed under suicient pressureto bubble through the opening it as the stopper i6 is manipulated and ofsuicient head to bubble up through the metal in reservoir tti to exert acleaning eect upon the metal in the reservoir. For instance if hydrogengas or carbon monoxide were thus passed upwardly through the reservoirit would have a tendency to clean oxides from the metal.

The gas supplied in the upper portion of the die casting apparatus maybe of sumcient pressure to pass downwardly between the metal and theinner walls of the die, thus continuously protecting the surface of thesolidifying metal from chemical action or from oxidation. At the sametime if the gas were hydrogen it would not detract greatly from the heatconductivity between the metal and the die as hydrogen is high in heatconductivity. At the same time this gas under pressure between the metalskin and the Walls of the die would tend to have a lubricating eect,that is it would reduce friction between the metal and the die. Areducing or non-oxidizing gas may be introduced at one or more of theconduits 10 in place of or in addition to the lubricant. i n i A suctionpump may be attached at 16 instead of the gas supply. This would createa vacuum in thelupper portion of the `die with consequent removal `ofoxygen and variation in characteris-a` i n be any cavity in the centerit would be closed tics of cast metal. y

Nothing has been said in detail with regard to the pinch rolls 28 orother apparatus to take care of the metal after it leaves the die assuch apparatus is `well known. Generally there would be suitable guidesand other'rolls to handle the metal after it passes from the diecastingapparatus.

I do notrestrict myself to either partially ori from the die; My processmay be operated either way but it is entirely feasible if the metalsection is not too thick to have the metal strip substan` tiallycompletely solid when it emerges from the 20 die.` The length yof thedie may be varied to obtain the result desired. l Y

While my description has been limited chiefly to the'casting of steel inthe form of aslab in `a. vertically arranged die, I desire it understoodthat I do not limit myself to any of these particulars.

" My improved process and apparatus may be used a for continuouslycasting other metals and other sections and with the die in variouspositions.

For instance, in Fig. 1 Ihave roughly illustrated a die section similarto Fig. 3 and having aninner die space for castings, rail section whichin practical operation would be slightly over size'so as to permit a nalrolling operation to exact size.

Y. The lubricant supply means is diagrammatically illustrated at 'll andperformsthe same function as the similar parts previously described.

The walls of die portion 26 will be shaped according to thecharacteristics of the metal being cast, always bearing in mind thatifthe metal 40 does not shrink enough to allow space for the lubricantillm, then the die walls will `flare outwardly enough to provide-such aspace.

In use, the process is started by placing a metal bar substantially ofthe cross section of the die exit end in the die with its projectingend-between the pinch rolls. Such a bar might be heated to weld with themetal iirst cast,or would carry projections at 'its inner end adapted tobond with the cast metal. Metal flow is then initiated bymanipulatingstopper I6 and, after" allowing time for the first lpoured metal tounite with the starter bar, the pinch rolls are started. t

'I'he speed of the pinch rolls is regulated as desired and the level ofthe metal in the die` controlled by manipulating stopper I6 as advisedbyf the conditions observed through the inspection window.l i e t i n 4My improved method f and apparatus may -be operated intermittently orcontinuously. The lato ter gives greater uniformity in the cast metal.

It results from the use ofthe above` described l process and apparatusthat metal may be continuously cast on a1commercial scale with very highquality as -to-internal physical characteristics and surfacecharacteristics of the castmetal.`

Theprotection afforded thewalls of the die gives i cast for anindefinite length of time because I` have overcome those difficultieswhich heretofore caused stoppage after comparatively short lengths hadbeen cast. A t

Where themetal cast is steel it has few or none `of the defects`heretofore found in usual casting methodsf For instance `there is nopipe in the `steel becausefthe center ofthe cast section is ncontinuously open to an unlimited supply of metal `at all times untilitis'congealed. The 'center is 5 protected against oxidation and ifthere should and welded bythe constricted exit end 2l of the die.Blow-holes arereducedito a minimum or.

entirely eliminated because ofthe quick freezing `10` of the metal Yandthe preventionr of oxidation of the metal so'that any small `holes ifformed will be welded together at `the exit end of the die. A very finecrystal `structure results from the fast freezing which makes for smallcrystals and the 15 uniform n casting conditions provide yuniformcrystal structure throughout the length of the metal strip. Because ofthe close control of the temperature of the metal throughout the entirey process the steel may becast from a mushy state 20 just above thesolidus if desired, thus further reducing the freezing time. The fastfreezing'lprovided gives little chance rforsegregation and the constantprogress of the freezing zone gives auniform distribution of whateveringredients settle 25 out. Non-metallic inclusions are practically lThere is no checking or cracks in the skin ofthe cast metal because ofthe smooth lubricated walls and the uniform movement duringfreezingprevents stresses inthe skin;` The constricted die 3" endi21prevents the pull of rolls 28 tearing-the metal in die portion 26. Thereare no scabs from splashes during pouringbecause the mold is filledslowl7;and uniformly without much dropping of metal and the upperportion`of the die is hot '4u enough to remelt splashes if any occur.

It should `be clearly understood that if the metal does not shrinksufficiently to provide space for efficiently introducing thevself-accommodating die lining material, then the die walls will be so4,; proportioned as to providethe requisite space. This may also be thecase if the die is made long enough to have the metal fullyl solidified`at its exit from the diei During the latter part of the passage ofmetal through Such a die, the shrink- 5u age may be very small. `Hereagain the die walls will be shaped to permit introduction of the plasticdie liningmaterial, regardless of the shrinkage ofthe cast metal.` i

There is good authority for `the theory that 55 considerable relativemovement takes place `between a die and metal cast init. 'There isexpansion and contraction of the die walis'due t0 i the effect ofthe hotmetallupon they colder walls. `'Ihere is expansion and contraction ofthe con- U0 `gealing metal also, because `wherever it touches a coldwall it will immediately shrink away only to later expand outwardly dueto reheating or due `to the ferrostatic pressure `of thestillmolteninterior even when the skin is ofsubstantial thick- 65 ness. p Myinvention for the rst time supplies `material between the skin'and dieadapted to ll all these interstices no matter how they vary so ,y thatthe skin of the congealing metal is supported and protected andthefwallsof the die are kept from directcontact withthe hot metal so i that thewalls are not galled or abraded or subjected to fire-cracks and hotmetal can not stick `to the wall. i

In certain of the claims applicant has defined .passing metal throughsaid die, said die being the die lining material as facilitating thecasting of the metal in the die. By this term facilitating" applicantmeans to cover material which supports the tender skin on the metalagainst sagging and rupture, which maintains suilicientheat conductivitybetween therskin and die wall to prevent reheating and remelting of theskin and maintains continuous -progressive cooling, which improves andprotects the metal surface, which protects the die surface, or which maylubrlcate the passage of the metal through th What I claim is:

1. Apparatus of the class described comprising a die having a passagetherethrough, means for passing molten metal into one end of saidpassage, said 'die having walls surrounding said passage and adapted toremove heat from said metal to i'orm a solid skin thereon within saidpassage, a refractory heat-conducting liner on said walls at theentrance end of said passage in contact with said molten metal forforming a rst skin thereon, said liner ending at that point where therst skin has formed, whereupon said metal shrinks away from the walls ofsaid die passage, and means for thereafter lling the lnterstices betweensaid metal skin and die walls with a heat-conducting material.

2. Apparatus as in claim 1 wherein said filling material has lubricatingproperties. A

3. The method of continuously casting metal comprising continuouslypassing metal through a hollow chilled die at a velocity permitting saiddie to congeal said metal from a molten to at least a partially solidstate and filling the space between said congealing metal and said diewith a finely divided solid material capable of remain ing solid duringthe casting operation and capable of accommodating itself to thelnterstices between the .cast metal and die wall.

4. Apparatus of the class described comprising a die having a passagetherethrough, means for passing metal through said die, said die beingconstructed to conduct heat away from said passage at a rate sufficientto form a solid skin on said metal at theexit end of said passage whensubstantially molten metal is fed to the entrance end of said passage,the relation between said congeallng metal and said die being such thatthere is a space between said metal and die at the point where the rstskin is formed on the surface of the metal, and means for supplying tosaid space at said point a powdered material facilitating the casting ofthe metal in said die.

5. Apparatus as in claim 4 including means for supplying to said space agas for protecting saidl powdered material against deterioration.

6. Apparatus of the class described comprising a substantially rigid diehaving a passage therethrough, means for passing metal through said die,said die being constructed to conduct heat away from said passage at arate suicient to form at least a, solid self-supporting skin on saidmetal at the exit end of said passage when molten metal is fed to theentrance end of said passage, means for supplying a graphitic compoundbetween said die and the metal passing i through it at a point where askin has formed on said metal insufficient alone to support the body ofmolten metal it encloses, said lining supporting said skin and hence thecolumn of metal, and said lining maintaining heat-conducting contactbetween said skin and die.

7. Apparatus of the class described comprising a die having a passagetherethrough, means for constructed to conduct heat away from saidpassage at a rate sufiicientto format least a solid skinx'on said metalat the exit endof said passage when substantially molten metal is fed tothe entrance end oi' said passage, and means for supplying between saidskin and die, at points spaced on said die, finely divided solidmaterial facilitating the casting of the metal'in said die and adaptedto nil all spaces between saidfskin and die,l said last named meansbeing adapted to vary the pressure at said spaced points, whereby thepressure on said material may be coordinated with the position andcondition of the solidifying metal in the die.

- the entrance end of said passage, there being a groove in the innerwall of said die located at a point where a skin has formed on saidmetal, and means for supplying a fiowable graphitic compound to saidgroove.

9. The method oi' continuously casting metal comprising continuouslypassing metal through a hollow chilled dielat a velocity permitting saiddie to congeal said metal from a molten to at least a partially solidstate whereby the metal forms an outer skin from contact with said dieduring the iirst portion of its passage therethrough, and thereaftercontinuously supplying between said skin and die a iinely divided solidmaterial capable of remaining solid during the casting operation andcapable of accommodating itself to the lnterstices between the castmetal and die wall, whereby to protect the walls of said die fromabrasion and galling, and to protect the surface of the congealing metalfrom run-outs and abrasion.

li). In the method of casting metal continuously comprising feedingmolten metal from a reservoir through a substantially gas-tightpassageway to one end oi a die which is open at both ends, whilechilling the metal in said die and 'drawing it out the other end of saiddie, the step of supplying .to said passageway a gas under sum cientpressure to cause some of it to pass into the molten metal in saidreservoir.

li. Apparatus of the class described comprising a die having a passagetherethrough, means for passing molten metal into one end of saidpassage, said die having walls surrounding said passage adapted toremove heat from said metal to form a solid skin thereon within saidpassage whereupon said metal shrinks away from the walls of said diepassage, and means positioned between the zone where said skin isnormally formed and the exit end of said die to fill the interstices'between said metal skin and die walls with a readily conformablematerial for supporting the solidied surface of the metal being castysurface and said walls from substantially the congealing sone to theexit end of Asazidiiiewith readily conformable material for supportingthe solidified surface of the cast metal away( n'om the die walls andfor facilitating the movement t of the metal out of the die.` i 13.Apparatus ot the class described compris lng a die having a passagetherethrough, for passing lmolten metal intoone end of said passage,said die having walls surroundingsaid ing a die having a passagetherethrough, means for passing molteameminto one end or nid passage,said die having walls surroimding said e adapted to remove heat fromsaid metal to form a solid skin thereon within saidpassage,

there being ports through said die walls and communicating with theinterior of said die between the zone where said `skin is formed andtheexit end orsaid die, and means for supplying to said ports anon-liquid lubricating material.

15. In the ymethod of continuously casting. metal which consists ofcontinuously feeding molten metal to one end of a hollow chilled die ata velocity permitting said die to congeal at least the outer surface ofthe metal `within the die', and continuously removing the chilled metalat the exit end of the die. the step comprising continuously introducinga non-liquid lubricating material between the vcongealed surface of themetal and the'wall of the die from the zone where said congealed surfacenormally forms to the exit end of the die.

NORMAN P.

